Method for forming ports in a sheet metal tube



Aug. 30, 1966 F. T. ANDERSON METHOD FOR FORMING PORTS IN A SHEET METAL TUBE 3 Sheets-Sheet 1 Filed Aug. 19, 1965 R N O O T S A R E v M m N A M T 1.5mm w Eom R n F mwmzxuik 352:

BY ines" &

ATTORNEYS Aug. 30, 1 6 F. "r. ANDERSON 3,269,165

METHOD FOR FORMING PORTS IN A SHEET METAL TUBE Filed Aug. 19, 1965 5 Sheets-Sheet 2 R FIG 2 I6 58 380 36 338 I4 I? EMIHBIHMDIMM HHIIHIEUHMIHBIHIIHMMIMMIU t FIG. 6

INVENTOR FRED T ANDERSON ATTORNEYS 5 Sheets-Sheet 3 INVENTOR ATTORNEYS Aug. 30, 1966 F. T. ANDERSON METHOD FOR FORMING PORTS IN A SHEET METAL TUBE Filed Aug. 19, 1965 FRED T. ANDERSON United States Patent 3,269,165 METHGD FUR FORMING PQRTS IN A SHEET METAL TUBE Fred T. Anderson, South Lyon, Mich, assignorof forty percent to Garnard W. Niece, South Lyon, T /11611:, and twenty percent to Clifton D. Hill, Northville, Mich. Filed Aug. 19, 1965, Ser. No. 489581 8 Claims. (Cl. 72326) This invention relates to a method of forming ports in a sheet metal tube.

The present application is a continuation-in-part of applicants application Serial No. 281,437, now abandoned, entitled, Sheet Metal Gas Burner and Method of Making Same, and filed May 20, 1963.

Numerous previous inventors have devised various means for piercing the wall of a sheet metal tube so as to form ports in the tube. However, none of these inventors has been able to devise an economical and convenient method for accurately dimensioning the ports so as to provide maximum utility. More specifically, in gas burner sheet metal tubes there is encountered the problem of dimensioning the axially aligned ports so as to provide maximum gas burner efiiciency throughout the entire axial length of the burner. According to the present method, ports are formed in the sheet metal tube by lancing through the wall of the tube along a predetermined first line in the circumference of the tube; sequentially lancing through the wall from the ends of said first line parallel second and third lines so as to form a tab hinged to the wall at a point longitudinally spaced from the first line and having its sides defined by the second and third lines. Then, the tab so formed is radially inwardly bent so as to form a fiat plane extending generally trans versely of the tube interior and defining an extended side of the port. Applicants method includes a formulization for accurate dimensioning of port width, as well as depth. The formation of burner ports in this fashion is economical and at the same time results in cool operation which maintains the temperature of the burner tube itself at a relatively low value. In addition, the lanced port construction enables the manufacture of a higher capacity burner in relation to the length of the burner.

Accordingly, it is an object of invention to provide a method for forming ports of accurate dimensions in sheet metal tubes.

Another object of the present invention is to provide a method for manufacture of a gas burner which is of economical construction and which at the same time possesses distinct advantages from the operational standpoint over gas burners of conventional design.

A further object of the invention resides in the provision of a very economical method of forming gas burner ports in a sheet metal burner.

More specifically, the invention contemplates a method for manufacture of a gas burner in the form of a sheet metal tube having a plurality of ports therein which are formed in the tube by a simple lancing operation.

In the drawings:

FIG. 1 is a series of schematic views showing the port tabs in cross section and illustrating the formula for determining port width according to the present invention;

FIG. 2 is a fragmentary sectional view of a gas burning heating device equipped with the burner constructed according to the present invention;

FIG. 3 is a top plan view of the burner;

FIG. 4 is a fragmentary sectional view showing the manner in which the burner ports are lanced in accordance with the present invention;

FIG. 5 is an enlarged fragmentary view of the burner tube;

FIG. 6 is a sectional view along the line 55 of FIG. 4;

3,26%,165 Patented August 36, 1966 FIGS. 7, 8, 9 and 10 are vertical sectional views of four modifications of lanced burner tubes in accordance with the present invention;

FIG. 11 is a sectional view along the line 1111 in FIG. 8;

FIG. 12 is a sectional view along the line 1212 in FIG. 9;

FIG. 13 is a sectional View along the line Iii-13 in FIG. 10;

FIG. 14 is a sectional view similar to FIG. 13 and showing a further modification of the invention.

Referring to the drawings, there is illustrated in FIG. 2 a gas heating device which includes an outer casing 10 which encloses an inner casing 12 forming the heat chamber of the device and a burner tube 14 which is constructed in accordance with the present invention. The tube 14 is formed of sheet metal and is closed at one end as at 16 and open at the other end as at 18. The closed end 16 of tube 14 is supported on outer casing 10 by a bracket 20. The open end of tube 14 has mounted thereon a supporting bracket 22 which in turn mounts an air baflie 24. A source of gas is supplied to the open end of tube 14 by means of a conduit 26 having a nozzle 28 at the end thereof located within the open end of tube 14. Casing 19 is provided with air inlet openings 30 adjacent the open end of tube 14 so as to supply the necessary air for combustion.

Referring now to FIGS. 4 and 8 which illustrate one form of burner tube constructed in accordance with the present invention, it will be observed that in this form of burner tube, the tube itself is of generally uniform circular cross section from one end to the other. The end 16 of the tube is closed by an end cap 32 and the open end 18 of the tube has a slight outward flare around its periphery as indicated at 34. The burner ports in the tube 14- are defined by a plurality of tabs 36 which are uniformly spaced apart lengthwise of tube 14 to provide spaced openings 38 therebetween.

FIG. 4 illustrates the manner in which the burner ports are formed in the tube in accordance with the present invention. In forming these burner ports, the tube is slidably supported on a mandrel or arbor 40, the end face 42 of which is ground flat and perpendicular to the longitudinal axis of the arbor. The peripheral edge 44 between the end face 42 and the cylindrical surface of arbor is relatively sharp and serves as a die for a punch 46. Punch 46 has a shank 48 and a tapered nose 51 which terminates in a relatively sharp edge 52 at the leading end of the punch. The nose 51 of punch 46 is of rectangular cross section. The rear face 54 of nose 56 lies in a plane perpendicular to the longitudinal axis of arbor 40 whereas the front face 56 of nose tapers upwardly and forwardly from the edge 5.2. In the arrangement illustrated, the taper on nose 50 above the curved leading end portion is about 15. The extent of this taper may be varied as will be apparent. Punch 46 is adapted to be vertically reciprocated by suitable means, not illustrated, and is supported such that the rear flat face 54 thereof is substantially coplanar with the leading end face 42 of arbor 40. The stroke of the punch and more specifically, the extent to which the nose 50 of the punch overlaps the arbor 40 can be varied as desired by conventional means, not illustrated.

In forming the lanced burner ports on tube 14, the openend of the tube is telescoped over the leading end of arbor 40 to a position such that the punch 46 is located in line with the location of the first burner port to be formed. Punch 46 is then caused to move downwardly through the wall of tube 14 and thus form the first aperture 38a. As the nose 50 engages the wall of the tube, it first lances a slit through the tube and as the punch continues to move downwardly, it lances a tab 58 and simultaneously bends the tab radially inwardly as shown in FIG. 4. The inclination of tab 58 is controlled by the stroke of punch 46 in relation to its taper. After the first aperture 38a is formed, the tube is indexed a predetermined amount (by means not illustrated) axially of arbor 40 so as to position the tube on arbor 40 at the desired location for forming the second aperture of the row of burner ports. The distance through which the tube is indexed is dependent upon the size of burner ports desired and the thickness of the tube wall. Thereafter, punch 46 is again caused to reciprocate to lance and bend the tab 36. Theoretically, in some instances, it would be desirable to have all the tabs 36 disposed in planes perpendicular to the longitudinal axis of tube 14. However, as the nose 50 of punch 46 advances through the wall of the tube, the tabs 36 are progressively lanced and progressively twisted. From the practical standpoint, the extent to which the tabs 36 are bent or twisted is short of that which would result in lancing the tabs completely from the tube or twisting them to such an extent that the tabs will break at the connecting corner portions 60 between the tabs and the tube wall (see FIGS. 5 and 6). The tube is progressively indexed and lanced in this manner until the desired length of row of burner ports is formed. Adjacent the last burner port, the tube is bent inwardly slightly as at 62 to form a baflle in advance of the row of burner ports. The bend at 62 has the effect of closing the first port slightly and tends to reduce the velocity of the gas flowing through the first port, thus reducing the tendency for the flame to blow off at the first port.

I have found that with tubes having a relatively small length-to-diameter ratio, there is a tendency for the gas to build up on pressure towards the closed end of the tube. This is undesirable in most instances since a larger flame will be produced at the ports adjacent the closed end of the tube than at the ports adjacent the open end of the burner tube. This problem can be solved very readily in several ways in accordance with the present invention. One method of solving this problem is illustrated in FIG. 7 wherein it will be seen that the tabs 36 are inclined a progressively lesser extent from the inlet end 18 of the tube towards the closed end 16 of the tube. At the inlet end 18, tabs 36 are inclined to the tube wall at an angle of almost 90 whereas at the closed end, the inclination of the tabs is about 45 Thus, the effective area of the ports adjacent the closed end 16 of the tube will be smaller than the effective area of the ports adjacent the open end 18 of the tube. The reduction in port area compensates for the increased pressure in a direction towards the closed end of the tube and thus, the flames emanating from all the ports will be of substantially the same size. The method of forming the burner tube illustrated in FIG. 7 is substantially the same as that shown in FIG. 4 with the exception, however, that the stroke of punch 46 is substantially shorter at the beginning of the lancing operation than at the end, means being provided on the lancing machine for pro gressively increasing the stroke of punch 46 each time the tube 14 is indexed.

In FIG. 9, the burner tube is designed to produce a flame of uniform height throughout the length of the row of burner ports by embossing the tube inwardly as at 64 at the portion thereof diametrically opposite the row of burner ports (FIG. 12) so that in effect, the cross section of the tube is progressively reduced from the inlet to the outlet end thereof. In this case, the end of the tube is closed by crimping as at 65. The cross sectional area of the burner tube can also be progressively decreased in a direction from the inlet to the outlet end thereof by fixing a baflle plate 66 running lengthwise within the tube as shown in FIGS. and 13.

The arrangement shown in FIG. 14 includes a generally V-shaped baffle plate 68 and two rows of burner punching holes in the tube.

ports instead of one as is illustrated in the other embodiments.

The burner tube of the present invention is economical from the standpoint of cost of manufacture. However, the feature of economy is not its only advantage. It will be observed, for example, that the successive ports or apertures 38 are spaced from one another only by the thickness of the tabs 36. This feature has several advantages. It enables a maximum of port area within a given length of burner tube without making the ports themselves excessively large. The close spacing of the ports as illustrated thus eliminates an excessive amount of intervening tube metal between successive ports which might have a tendency to become heated and thus reduce the efficiency of the burner. The close spacing of the ports produces in effect a continuous ribbon-type flame which assures the continuity of ignition.

It will also be observed that the tabs 36 impart depth to the ports. This is important from the standpoint of flash back which is a common problem where the ports are relatively shallow as would be the case, for example, where ports are formed in a sheet metal tube by merely While obtaining these advantages, it will be observed that the flames emanating from the ports are substantially vertical, the more erect flames giving a better flame pattern and reducing the wiping action of the flames on the burner top wall and resulting in cooler operation. The cooler operation also tends to inhibit flash back. This cooler operation re sulting from the disposition of tabs 36 so that they are substantially vertical is very important because the close spacing of the adjacent flames results in a higher capacity per unit length of the burner which increases the operating temperature of the burner. This in turn heats and expands the gas flowing into the burner tube causing a back pressure or a choking effect which tends to reduce injection of primary air and lowers the combustion efficiency. In applicants burner, this deleterious effect is minimized by producing the more erect flames and by placement of the burner ports along the topmost surface of the burner tube. Where additional capacity per unit length of burner tube is required, multiple parallel rows of lances as shown in FIG. 14 can be employed.

Another advantage of the present invention resides in the ability to control the size of burner ports as desired. It will be appreciated that the size of the burner ports can be controlled in several ways. For example, the burner ports can be made of larger or smaller size by making the cross sectional area of the nose portion 50 of punch 46 greater or smaller. Likewise, the size of the burner ports can be made smaller with any given punch 46 by simply shortening the stroke of the punch and thus inclining the tabs 36 to a lesser extent as is illustrated in FIG. 7. In this connection, it will be appreciated that if the length-to-diameter ratio of the burner tube is very large, a point may be reached where the gas pressure at the closed end of the burner tube due to wall friction is actually less than the gas pressure at the inlet end of the tube. In such cases, the stroke of punch 46 may be controlled so that it is greater at the closed end of the tube than at the inlet end of the tube, the result being that the tabs adjacent the closed end of the tube will be more vertically disposed than at the inlet end of the tube and the ports will therefore be of greater size at the closed end of the tube than at the inlet end of the tube. The method for formulating port width is illustrated in FIG. 1. Port depth is effectively controlled for most practical purposes by varying the angle of inclination of the port tabs from 45 to However, it is found that when the tab 36 bottoms are not perpendicular to the tube axis, but staggered as in the two top portions of FIG. 1, there is provided an enhanced cooling effect. As a result, the inclined tabs can provide the cooling effects of a port having vertical walls.

It is apparent that as the port width is diminished by reducing the angle of inclination of the tabs, the depth of the ports is also diminished. However, experience has shown where the tabs are slanted, even to the extent of about 45 as shown at the top of FIG. 1, the effective port depth is still suflicient to insulate the gas flowing into the ports from the flames issuing from the ports. This result is achieved in part because of the wiping effect of the gas on the slanted tabs. The burner of this invention thus operates at a relatively cool temperature even when the tabs defining the ports are slanted as distinguished from extending perpendicular to the axis of the burner tube. The cool operation which thus results promotes eflicient burning and minimizes the tendency for flash-back.

In many applications, it will be appreciated that the eifect of the wall friction will overcome the tendency for the gas pressure to build up at the closed end of the tube and thus, there is no need to either reduce the cross sectional area of the tube or to reduce the port size in a direction towards the closed end of the tube. In such applications, the burner tube is not restricted in cross section and all the tabs 36 are uniformly inclined as shown in FIGS. 4 and 8. However, in any event, the baffle 62 should preferably be formed at the beginning of the row of ports so that an excessive amount of gas is not caused to issue from the first burner port in the row. Baflle 62 not only reduces the area of the first port in the row but also tends to deflect the combustible mixture slightly away from the first few ports in the row and thus reduce the pressure thereon so as to produce a more uniform flame throughout the row of burner ports.

Although I have illustrated the formation of the burner ports by bending the tabs 36 inwardly, it will be appreciated by those skilled in this art that the arrangement shown in FIG. 4 can be reversed. Namely, the punch member 46 can be arranged within the burner tube 14 and the mandrel formed as a sleeve surrounding the burner tube so that tabs 36, instead of being bent inwardly, are lanced and bent in an outward direction. Likewise, while it is expedient to produce such burners from standard tubing of round cross section, it will be appreciated that the burner port illustrated can be fabricated on sheet metal in the flat and therefore, the burner tube may have any desired form or cross section.

I claim:

1. Method of forming ports in the Wall of a sheet metal gas burner tube, comprising:

(A) lancing through said wall along a predetermined first line substantially normal to the longitudinal axis of tube;

(B) sequentially lancing through said wall from the ends of said first line, second and third lines parallel to the axis of said tube so as to form a tab hinged to said wall at a point longitudinally spaced from said first line and having its sides defined by said second and third lines; I

(C) radially inwardly bending said tab so as to form a flat plane extending generally transversely of said tube and defining an extending side of said port;

(D) forming a plurality of such ports in axially aligned spaced relationship Within the wall of said tube;

(E) calculating the width of said ports according to the following formula where: W=port width, L: angle of inclination of the tab, T=the sheet metal tube thickness, S=the spacing between ports W=S-sin L-T and (F) controlling port depth by varying the angle of inclination of said tabs from a position of being bent approximately 45 inwardly of the wall of said sheet metal tube to a position where said tab is bent to approximately inwardly with respect to the wall of said tube.

2. Method as in claim 1, including controlling port depth by varying the angle of inclination of said tabs from a position of being bent approximately 45 inwardly of the wall of said sheet metal tube to a position where said tab is bent to approximately 90 inwardly with respect to the wall of said tube.

3. Method as in claim 1, including limiting port width to a dimension less than the thickness of said sheet metal.

4. Method as in claim 1, including regulating spacing between ports to a distance at least as great as the thickness of said sheet metal.

5. Method of making a gas burner which includes the step of forming a row of gas burning ports therein which comprises:

(A) forming the body of the burner as a sheet metal tube;

(B) supporting the tube internally on an arbor such that the leading end of the arbor terminates inwardly of one end of the tube;

(C) driving a taper-pointed punch through the wall of the tube utilizing the leading end of the arbor as a die for the punch;

(D) then, shifting the tube axially on the arbor a predetermined distance greater than the wall thickness so that the sheared edge of the previously formed. opening is spaced from the end of the arbor;

(B) then again driving the punch through the wall of the tube and utilizing the tapered end of the punch on its punching stroke to bend the tab between the two shear lines into a generally flat plane extending transversely of the plane of the wall member and continuing said operation until a row of ports of desired length is formed.

6. Method called for in claim 5, including the step of controlling the stroke of the punch in a direction inwardly of the tool to control the extent of bending of said tabs.

7. Method called for in claim 6, wherein the stroke of the punch is controlled such that the tabs are bent toa position wherein they are generally perpendicular to the plane of the wall.

8. Method called for in claim 6, wherein the stroke of the punch is controlled such that the tabs are bent a progressively lesser extent from one end of the row to the other.

References Cited by the Examiner UNITED STATES PATENTS 410,723 9/1889 Wiesing 72-326 1,773,522 8/ 1930 Delery 72-326 2,135,810 111/1938 Germonprez 98110 2,222,081 1 1/ 1940 Leigh 72458 2,613,743 10/ 1952 Bangerter 72325 2,755,851 7/1956 Dow et al. 15-8114 FOREIGN PATENTS 586,223 10/1933 Germany.

1,024,473 2/ 1958 Germany.

CHARLES W. LANHAM, Primary Examiner.

W. H. JUST, Assistant Examiner. 

1. METHOD OF FORMING PORTS IN THE WALL OF A SHEET METAL GAS BURNER TUBE, COMPRISING: (A) LANCING THROUGH SAID WALL ALONG A PREDETERMINED FIRST LINE SUBSTANTIALLY NORMAL TO THE LONGITUDINAL AXIS OF TUBE; (B) SEQUENTIALLY LANCING THROUGH SAID WALL FROM THE ENDS OF SAID FIRST LINE, SECOND AND THIRD LINES PARALLEL TO THE AXIS OF SAID TUBE SO AS TO FORM A TAB HINGED TO SAID WALL AT A POINT LONGITUDINALLY SPACED FROM SAID FIRST LINE AND HAVING ITS SIDES DEFINED BY SAID SECOND AND THIRD LINES; (C) RADIALLY INWARDLY BENDING SAID TAB SO AS TO FORM A FLAT PLANE EXTENDING GENERALLY TRANSVERSELY OF SAID TUBE AND DEFINING AN EXTENDING SIDE OF SAID PORT; (D) FORMING A PLURALITY OF SUCH PORTS IN AXIALLY ALIGNED SPACED RELATIONSHIP WITHIN THE WALL OF SAID TUBE; (E) CALCULATING THE WIDTH OF SAID PORTS ACCORDING TO TO FOLLOWING FORMULA WHERE: W=PORT WIDTH, L= 